Methyl Acetate Purification via Polyol Reaction
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Solution Overview
Problem
The challenge in the methanol carbonylation process is the presence of aldehyde impurities in methyl acetate supplies, which complicate the production of acetic acid and are difficult to separate due to their close boiling points with methyl acetate, leading to increased impurity levels in the acetic acid product.
Innovation Solution
Reacting aldehyde impurities in methyl acetate with a polyol to form cyclic acetals, which can be readily isolated by distillation, thereby purifying the methyl acetate supply for use in carbonylation reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If aldehyde impurities are removed from methyl acetate supply, then the purity of acetic acid product is improved, but the separation difficulty increases due to close boiling points
Solution Approach 1:
The patent uses polyols as intermediary reagents that react with aldehyde impurities to form cyclic acetals. These cyclic acetals have significantly different physical properties (boiling points) from methyl acetate, enabling easy separation through distillation. The polyol acts as a mediator that transforms the difficult-to-separate aldehyde into an easily separable cyclic acetal derivative.
Solution Approach 2:
The patent changes the chemical parameters of the aldehyde impurity by reacting it with polyol to form a cyclic acetal with different boiling point characteristics. This parameter change (from aldehyde to cyclic acetal) fundamentally alters the separability of the impurity from methyl acetate, allowing effective removal through standard distillation processes.
2Productivity
If water concentration is lowered in methanol carbonylation, then carbonylation rate and acetic acid yield increase, but aldehyde formation increases
Solution Approach 1:
The patent applies preliminary action by removing aldehyde impurities from the methyl acetate supply before it enters the carbonylation reactor. By pre-treating the methyl acetate with polyol to convert aldehydes to cyclic acetals and removing them, the system enables operation at lower water concentrations without the penalty of increased aldehyde formation in the final product.
Solution Approach 2:
The patent converts the harmful effect of aldehyde formation (which worsens at lower water concentrations) into a beneficial situation. By adding polyol that selectively reacts with aldehydes to form easily removable cyclic acetals, the system can operate at optimized low water concentrations while still achieving high product purity through the subsequent aldehyde removal step.
3Ease of operation
If aldehyde impurities are present in methyl acetate supply, then the carbonylation process is complicated, but separation by distillation is ineffective due to close boiling points
Solution Approach 1:
The patent introduces polyol as an intermediary substance that selectively reacts with aldehyde impurities in the methyl acetate supply. This reaction forms cyclic acetals that can be easily separated from methyl acetate by distillation due to their different boiling points, thereby simplifying the overall purification process while maintaining high product purity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively removes greater than 99.9% of aldehyde impurities, reducing their level in the acetic acid product and enhancing carbonylation efficiency by utilizing the purified methyl acetate supply.
Implementation Method 1
reacting aldehyde impurities with a polyol to form cyclic acetals
Implementation Method 2
cyclic acetals that can be readily isolated from the methyl acetate supply by, e.g., distillation
Data Source
AI summary
Disclosed is a method for removing aldehyde impurities from a methyl acetate supply. The method comprises reacting the methyl acetate supply with a polyol and converting the aldehyde impurities to cyclic acetals. The acetals are subsequently removed from the methyl acetate supply by, e.g., distillation. The purified methyl acetate supply is used for carbonylation to produce acetic acid.